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Mathematics Colloquium


Contact: Federico Ardila
Time and Location: Wednesdays, 4:10-5:00 pm in Thornton Hall 211.
Refreshments: 3:30 pm in Thornton Hall 935.

Past colloquia: videos and abstracts.


Dates for Spring 2008: Feb 6 Feb 20 March 6,7 Mar 19 Apr 9 May 7
























































February 6, 2008

Sergey Fomin

University of Michigan

TITLE: Cluster Algebras.
ABSTRACT: Cluster algebras arise in various algebraic and geometric contexts, with combinatorics providing a unifying framework. My presentation of the basic definitions and results of this emerging theory will be guided by two sets of examples: coordinate rings of classical algebraic varieties, and cluster algebras associated with bordered oriented surfaces with marked points.
4:10 PM in TH 211
refreshments served in TH 935 at 3:30 PM


February 20, 2008

Francisco Santos

Universidad de Cantabria, Santander, Spain

TITLE: Graphs of triangulations.
ABSTRACT: I will give an introduction to the "graph of flips" between triangulations of a polytope (its definition, its connections to algebraic geometry, geometric combinatorics, and combinatorial topology) and review the disconnected graphs of flips that I have constructed in recent years, in dimensions five and six.
4:10 PM in TH 211
refreshments served in TH 935 at 3:30 PM


March 6, 2008

Pamela Fong Symposium

Richard Stanley

Massachusetts Institute of Technology

TITLE: A survey of plane tilings.
ABSTRACT: We will survey some of the highlights of the theory of plane tilings, focusing on tiling a bounded region of the plane with finitely many tiles. A standard example, though not very mathematical, is a jigsaw puzzle. We consider such questions as the following: (1) Is there a tiling? (2) How many tilings are there? (3) About how many tilings are there? (4) Is a tiling easy to find? (5) Is it easy to prove or to convince someone that a tiling doesn't exist? (6) What does a typical tiling look like? We point out some interesting connections between tilings and such topics as computer science, continued fractions, probability theory, and mathematical logic.
4:10 PM in HSS 317


March 7, 2008

Pamela Fong Symposium

Richard Stanley

Massachusetts Institute of Technology

TITLE: Increasing and decreasing subsequences.
ABSTRACT: A subsequence of a permutation of 1,2,..., n is *increasing* if its elements appear in increasing order. For instance, 4578 is an increasing subsequence of 43571826. A *decreasing subsequence* is similarly defined. We will survey the subject of increasing and decreasing subsequences, focusing on what can be said about the longest increasing and longest decreasing subsequence of a permutation. Topics will include (a) relationship to Young tableaux and the famous RSK algorithm, (b) the asymptotic behavior of the length of the longest increasing subsequence (due to Baik, Deift, and Johansson), (c) connections with random matrix theory, and (d) an extension of the theory from permutations to complete matchings.
4:10 PM in SCI 210


March 19, 2008

Mariana Ferreira

Department of Anthropology

San Francisco State University

TITLE: The Mathematics of Gift-Exchange in the Brazilian Amazon.
ABSTRACT: This presentation discusses how values and symbolic properties of both gift exchange and capitalist economics structure arithmetic dilemmas in the Brazilian Amazon. By articulating principles of the gift with those of capitalist economic action, Indigenous Peoples highlight the ways in which mathematical knowledge is constituted in everyday practice, challenging functional assumptions about cognition and schooling. Gift-exchange also informs Indigenous environmental theories about the collective allocation of land and natural resources. Successful Indigenous GIS-GPS map-making initiatives in Central-Brazil rely on community-based participatory research methodology to advocate for human rights and propose new insights into how mathematical knowledge is built throughout history in different socio-cultural environments.
4:10 PM in TH 211
refreshments served in TH 935 at 3:30 PM


April 9, 2008

Steven Krantz

Washington University

TITLE: Analysis on the Worm Domain.
ABSTRACT: In joint work with Marco Peloso, we study the Bergman kernel on the classical worm domain of Diederich and Fornaess. A detailed asymptotic expansion for the worm is obtained. This yields important results about mapping properties of the Bergman projection, and also important irregularities of the Bergman kernel and projection.
Prerequisites for this talk are minimal. A graduate student with a course in complex variables should be able to understand the key ideas.
4:10 PM in TH 211
refreshments served in TH 935 at 3:30 PM


May 7, 2008

Gitta Kutyniok

Stanford University

TITLE: Geometric Separation via l_1 Minimization and Sparsity.
ABSTRACT: Modern data is often composed of two (or more) morphologically distinct constituents - for instance, pointlike and curvelike structures in astronomical imaging of galaxies. Although it seems impossible to extract those components - as there are two unknowns for every datum - suggestive empirical results have already been obtained. In this talk we first give a general introduction into geometric separation problems and discuss the recent avalanche of work which uses the methodology of l_1 minimization and sparsity. We then present the first theoretical approach to the geometric separation of pointlike and curvelike structures based on the overcomplete systems of radial wavelets and curvelets or of orthonormal wavelets and shearlets which sparsify the different components. As our main result we prove that using a particular form of l_1 minimization as the decomposition technique achieves in fact arbitrarily perfect separation of pointlike and curvelike structures. This is joint work with David Donoho (Stanford University).
4:10 PM in TH 211
refreshments served in TH 935 at 3:30 PM




Previous semesters.

  • Fall 2007.
  • Spring 2007.
  • Fall 2006.
  • 2005-2006.
  • 2004-2005.
  • 2003-2004.

    Fong Symposia.
  • Richard Stanley, 2007-2008.
  • Carl Pomerance, 2006-2007.
  • Efim Zelmanov, 2004-2005.



  • Mathematics
    San Francisco State
    Thornton Hall 937 · 1600 Holloway Ave · San Francisco, CA 94132
    Email: statmath@math.sfsu.edu · Telephone: (415) 338-2251 · Fax: (415) 338-1461